Research On Interference Suppression And Maneuvering Target Detection In Skywave Over-the-horizon Radar

Skywave over-the-horizon radar(OTHR) has many advantages, for example, the long alarm distance, wide monitoring scope, high cost-effectiveness, outstanding capability of anti-raid of low altitude and anti-stealth. Therefore, OTHR is valued by many world powers. It has been widely used in the area of national defense and civilian areas like sea condition monitoring and narcotics smuggling.Although OTHR has many advantages compared with traditional radars, it is faced with many challenges because of the special working system and the complicated environment. The challenges are: the strong interference and clutter in radar echoes, which will seriously affect the extraction of target signal and target parameters estimation, and the expansion of doppler spectrum of high-speed maneuvering air target, which will increase the difficulty of target detection and parameters estimation.Considering the challenges in OTHR, RFI(radio frequency interference) suppression, transient interference suppression and maneuvering target detection are studied in this thesis. The main content is given as follows:(1) Research on RFI suppression algorithmThe cause, features and the influence of RFI in OTHR are studied. Presents a RFI suppression algorithm based on whitening thought, but this algorithm will destroy sea clutter and targets signal. To solve the problem, proposes a novel RFI suppression algorithm based on interference culling in frequency domain. The algorithm can suppress RFI effectively without the damage to sea clutter and targets signal. Simulation results verify the conclusion.(2) Research on transient interference suppression algorithmThe mechanism, characteristics and echo features of two kind of common transient interference(the meteor trail echo and lightning impulse interference) in OTHR are studied. Presents two classic transient interference suppression algorithm(the algorithm based on AR model linear prediction and the algorithm based on the adaptive gaussian basis representation method). Processes the real data containing the meteor trail echo and lightning impulse interference by the two algorithms respectively. Based on the processing result, the advantages and disadvantages of the two algorithms are analyzed.(3) Research on maneuvering target detection algorithmA novel maneuvering target detection algorithm based on cubic phase function is proposed. Compared with the maneuvering target detection algorithm based on high-order ambiguity function, the proposed algorithm reduces the operation number of order reduction of nonlinear phase. The proposed algorithm reduces the loss of the signal to noise ratio, therefore it needs lower input SNR. The advantages are verified by the simulation data and real data. Another maneuvering target detection algorithm based on the improved time-frequency analysis method is proposed. Compared with the maneuvering target detection algorithm based on traditional time-frequency analysis method, the proposed algorithm has lower SNR threshold and higher precision of parameter estimation. It also can suppress the cross-term interference caused by multiple maneuvering targets. The processing of simulation data and real data verifies these advantages of the proposed algorithm.